The significant benefit of 24 hour ambulatory monitoring, especially in gastroenterology where diseases are sometimes asymptomatic, is that monitoring systems provide more information thereby improving diagnostic ability. Several systems have addressed the significance of real time physiologic measurements, however, they have limited application due to: probe technological problems, the inability of current systems to interface with different types of probes and the lack of cost effectiveness per procedure. We propose to purchase an existing portable computer and to develop interfaces for commercially available transducers, initially pH and pressure. The interfaces will communicate to the computer by standard protocols so that development of new probes and interfaces will require only software changes in the portable computer. The system will be capable of handling up to four different types of probes, and provide various forms of data output. This will allow ReTech to develop additional medical and non-medical uses for the system in the future. The multi-use design of our system will significantly be more cost effective per procedure. Upon completion of phase I, our system will have an immediate market potential in cardiology, urology, obstetrics, gynecology and gastroenterology. Dr. Tucker and Mr. Sievert have had several mutual publications and seven years of research collaboration in the area of gastroenterology and in the application of microcomputers in medicine; both are well qualified to fulfill this project. Mr. Macht has several years experience in the design and construction of portable data recorders.